Chemical mechanical planarization pads via vat-based production

ABSTRACT

A chemical mechanical polishing (CMP) pad includes a polishing portion formed using a vat-based additive manufacturing process. The polishing portion includes a polymer material with a first elastic modulus. In some embodiments the polishing portion is disposed on the backing portion. The backing portion may have a second elastic modulus. The second elastic modulus may be less than the first elastic modulus.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 of U.S.Provisional Application Ser. No. 62/844,196, filed May 7, 2019,entitled, “Chemical mechanical planarization pads via continuous liquidinterface production” and U.S. Provisional Application Ser. No.62/926,192, filed Oct. 25, 2019, entitled, “Chemical mechanicalplanarization pads with constant groove volume,” each of which is herebyincorporated by reference.

TECHNICAL FIELD

This disclosure generally relates to polishing pads used in chemicalmechanical polishing, and more specifically to chemical mechanicalpolishing pads prepared via vat-based production.

BACKGROUND

An integrated circuit is typically formed on a substrate by thesequential deposition of conductive, semi-conductive, and/or insulativelayers on a silicon wafer. A variety of fabrication processes requireplanarization of at least one of these layers on the substrate. Forexample, for certain applications (e.g., polishing of a metal layer toform vias, plugs, and lines in the trenches of a patterned layer), anoverlying layer is planarized until the top surface of a patterned layeris exposed. In other applications (e.g., planarization of a dielectriclayer for photolithography), an overlying layer is polished until adesired thickness remains over the underlying layer. Chemical-mechanicalplanarization (CMP) is one method of planarization. This planarizationmethod typically involves a substrate being mounted on a carrier head.The exposed surface of the substrate is typically placed against apolishing pad on a rotating platen. The carrier head provides acontrollable load (e.g., a downward force) on the substrate to push itagainst the rotating polishing pad. A polishing liquid, such as slurrywith abrasive particles, can also be disposed on the surface of thepolishing pad during polishing.

SUMMARY

One objective of a chemical mechanical planarization process is toachieve a high polishing uniformity. If different areas on the substrateare polished at different rates, then it is possible for some areas ofthe substrate to have too much material removed (“overpolishing”) or toolittle material removed (“underpolishing”). Conventional polishing pads,including standard pads and fixed-abrasive pads, can suffer from theseproblems. A standard pad may have a polyurethane polishing layer with aroughened surface and may also include a compressible backing layer. Afixed abrasive pad has abrasive particles held in a containment mediaand is typically supported on an incompressible backing layer.

These conventional polishing pads are typically prepared by molding,casting or sintering polyurethane materials. Molded polishing pads mustbe prepared one at a time (e.g., by injection molding). For castingpolishing pads, a liquid precursor is cast and cured into a “cake,”which is subsequently sliced into individual pad sections. These padsections must then be machined to a final thickness. Polishing padsprepared using conventional extrusion-based processes generally lackdesirable properties for CMP (e.g., are too brittle for effective CMP).This disclosure provides polishing pads, and methods of theirmanufacture, that facilitate improved polishing uniformity to meet theincreasingly challenging polishing requirements of new integratedcircuit designs.

In one embodiment, a chemical mechanical polishing (CMP) pad includes apolishing portion formed using a vat-based additive manufacturingprocess. The polishing portion includes a polymer material with a firstelastic modulus. In some embodiments, the polishing portion includes apolishing surface. In some embodiments, the polishing surface includesat least one of grooves, pores, or a microstructure. In someembodiments, a density of the polishing portion is in a range from 0.3to 0.9 grams per centimeter cubed (g/cm³). In some embodiments, thepolishing portion includes polyurethane. In some embodiments thepolishing portion is disposed on a backing portion. In some embodiments,the backing portion has a second elastic modulus. In some embodiments,the second elastic modulus is less than the first elastic modulus. Insome embodiments, the backing portion is formed using the vat-basedmanufacturing process. In some embodiments, the backing portion includesat least one of a nonporous layer, a porous layer, or a latticestructure. In some embodiments, the polishing portion and the backingportion may be attached without the use of an adhesive.

In another embodiment, a chemical mechanical polishing pad includes asurface portion of a first material. The surface portion includes aplurality of grooves. A first portion of the grooves are exposed grooveslocated at a surface of the chemical mechanical polishing pad. A secondportion of the grooves are buried grooves embedded below the surface ofthe chemical mechanical polishing pad, such that, during use of thechemical mechanical polishing pad, one or more of the buried grooves areexposed at the surface.

BRIEF DESCRIPTION OF FIGURES

To assist in understanding the present disclosure, reference is now madeto the following description taken in conjunction with the accompanyingdrawings, in which: FIG. 1 is a diagram of an example system forchemical mechanical planarization (CMP);

FIGS. 2A-2C are diagrams of example polishing pads, according toillustrative embodiments of the present disclosure;

FIG. 3 is a diagram of an example polishing surface of a polishing pad,according to an illustrative embodiment;

FIG. 4 is a diagram of an example polishing pad, according to anillustrative embodiment;

FIGS. 5A and 5B are diagrams of an example polishing pad according to anillustrative embodiment

FIG. 6A-6D are diagrams of an example polishing pad according to anillustrative embodiment;

FIGS. 7A-7C are diagrams illustrating polishing pads with buriedgrooves, according illustrative embodiments of this disclosure;

FIGS. 8A-8E are diagrams illustrating example polishing pads with buriedgrooves and channels, according to various illustrative embodiments.

FIG. 9 is a diagram illustrating an example polishing pad withrelatively large buried grooves configured to act as slurry reservoirs;

FIGS. 10A and 10B are diagrams illustrating example polishing pads withchannels vertically connecting buried grooves in order to provide slurryreservoirs; and

FIG. 11 is a flowchart illustrating an example method of preparing andusing any of the polishing pads described in this disclosure; and

FIGS. 12A and 12B are diagrams illustrating two different orientationsfor preparing polishing pads using continuous liquid interfaceproduction.

DETAILED DESCRIPTION

It should be understood at the outset that, although exampleimplementations of embodiments of the disclosure are illustrated below,the present disclosure may be implemented using any number oftechniques, whether currently known or not. The present disclosureshould in no way be limited to the example implementations, drawings,and techniques illustrated below. Additionally, the drawings are notnecessarily drawn to scale.

The present disclosure recognizes that conventional processes formanufacturing CMP polishing pads, including pads prepared viaextrusion-based printing, (i) suffer from low throughput and lowreproducibility; (ii) cannot be used to prepare pads with complex,multi-scale three-dimensional porous structures; and (iii) are oftenincompatible with materials which have desired chemical and mechanicalproperties for CMP. Moreover, in order to provide uniform polishing, apolishing pad should form a uniform contact with the substrate beingpolished, such that uniform pressure can be applied across the substratesurface. Variation in pad thickness can result in non-uniform pressureacross the substrate surface. Even small variations in thickness maylead to variations in the applied pressure, and hence non-uniformremoval during polishing as well as increased defects (e.g.,micro-scratches) on the substrate surface. The polishing pads describedherein provide more uniform polishing than is possible usingconventional polishing pads.

The present disclosure further recognizes that a polishing pad withimproved chemical and mechanical properties may be efficiently producedusing a vat-based additive manufacturing process. Vat-based additivemanufacturing generally involves the sequential photopolymerization ofthin layers of a volume of a liquid precursor to form an object. Theliquid precursor is contained in a vessel (e.g. vat). The vat may be anysuitable container capable of holding a sufficient amount of the liquidprecursor to supply the build region. For example, a thin film of aliquid precursor (e.g., a liquid UV sensitive prepolymer, e.g., aphoto-active resin) may be exposed to spatially patterned UVirradiation. Regions (e.g. build region) of the precursor that areexposed to UV irradiation are polymerized to form a thin solid layerthat has a structure that is determined by the pattern of the UVirradiation. Each layer is about 25-100 micrometers thick and isdeposited on the previous layers which are adhered to a movable buildplatform. The build platform is moved such that the polishing pad layeris continuously formed using patterns of UV irradiation, resulting inthe precise layer-by-layer formation of a polymer structure with adesired design and dimensions. Examples of such processes includecontinuous liquid interface production (CLIP) and high-area rapidprinting (HARP).

Chemical Mechanical Planarization System

FIG. 1 illustrates a system 100 for performing chemical mechanicalplanarization. System 100 includes a CMP pad 102 (also referred to as a“polishing pad”) which is placed on or attached to a platen 104. Forexample, an adhesive layer (not shown) may be used to attach thepolishing pad to the platen 104. The platen 104 can generally be rotatedduring chemical mechanical planarization. A wafer 106 (e.g., a siliconwafer with or without conductive, semi-conductive, and/or insulativelayers, as described above) is attached to a head 108 of a rotatablechuck. The wafer 106 may be attached using vacuum and/or a reversibleadhesive (e.g., an adhesive that holds the wafer 106 in place duringchemical mechanical planarization but allows the wafer 106 to be removedfrom the head 108 after chemical mechanical planarization). Asillustrated in FIG. 1, a pressure may be applied to the wafer 106 duringchemical mechanical planarization (e.g., to facilitate contact betweenthe surface of the wafer 106 and the polishing pad 102).

Example polishing pads 102 are illustrated in FIGS. 2A-10B and describedin greater detail with respect to these figures below. The polishing pad102 generally has a circular or approximately cylindrical shape (i.e.,with a top surface, a bottom surface, and a curved edge). The polishingpad 102 may comprise polyurethane, such as a flexible polyurethane or arigid polyurethane. Examples of compositions used to prepare examplepolishing pads 102 are described in greater detail below. In someembodiments, the compositions include one or more porogens. The porogensmay be particles (e.g., microspheres) which expand in volume whenheated. The porogens may cause the formation of pores in the polishingpad 102, which may improve pad performance, as described below withrespect to FIG. 3 and TABLE 1. Polishing pad 102 may have anyappropriate thickness and any appropriate diameter (e.g., to be employedwith a CMP system such as system 100, described above). For instance,the thickness of a polishing pad 102 may range from about 0.5millimeters to greater than 5 centimeters. In some embodiments, thethickness of the polishing pad may be in a range from 1 millimeter to 5millimeters. Vat-based manufacturing processes may be used to preparepolishing pads 102 that are thick, and these thick polishing pads 102can include more complex structures (e.g., a larger number of layers ofburied grooves) than was possible using previous technology. Polishingpad diameter is generally selected to match or be just smaller than, thediameter of the platen 104 of the polishing system 100 used. Thepolishing pad 102 generally has a uniform thickness (e.g., a thicknessthat varies by no more than 50%, 25%, 20%, 10%, 5%, or less across theradial extent of the polishing pad).

The vat-based manufacturing processes described in this disclosurefacilitate the preparation of a pad 102 with improved properties forchemical mechanical planarization. Examples of the polishing pad 102 aredescribed in greater detail below with respect to FIGS. 2A-10B. FIGS.2A-2C describe the structure of example polishing pads 102 with apolishing portion and an underlying backing portion. FIG.

3 illustrates a portion of a polishing pad 102 with a porous structure.The pad 102 may have a compressibility (e.g., elastic modulus) thatvaries along the radius of the pad to provide improved planarization, asdescribed in greater detail below with respect to FIG. 4. FIG. 4. Thepresence of buried grooves and/or channels provides several benefitssuch as improved planarization uniformity, extended pad lifetime, asdescribed in greater detail below with respect to FIGS. 5A to 10B.

A slurry 110 may be provided on the surface of the polishing pad 102before and/or during chemical mechanical planarization. The slurry 110may be any appropriate slurry for planarization of the wafer type and/orlayer material to be planarized (e.g., to remove a silicon oxide layerfrom the surface of the wafer 106).

The slurry 110 generally includes a fluid and abrasive and/or chemicallyreactive particles. Any appropriate slurry 110 may be used. For example,the slurry 110 may react with one or more materials being removed from asurface being planarized. Certain embodiments of the polishing padsdescribed in this disclosure provide for the removal of expended slurry110 (i.e., slurry 110 in which active materials have been largelyconsumed) away from the surface being planarized and/or for thereplenishment of fresh slurry 110 near the surface being planarized(see, e.g., FIGS. 5A-5B, 6A-6D, and 8E).

A conditioner 112 is a device which is configured to condition thesurface of the polishing pad 102. The conditioner 112 generally contactsthe surface of the polishing pad 102 and removes a portion of the toplayer of the polishing pad 102 to improve its performance duringchemical mechanical planarization. For example, the conditioner 112 mayroughen the surface of the polishing pad 102. If the polishing pad 102is one of the unique polishing pads described in this disclosure withburied grooves, the conditioner 112 may expose buried grooves which areembedded within the polishing pad 102. As described further below, theunique polishing pads described in this disclosure may reduce or removethe need to use conditioner 112 because the lifetime of the polishingpads described in this disclosure are extended compared to those ofconventional polishing pads.

Example Polishing Pads

FIGS. 2A-2C illustrate exemplary polishing pads 200 of the presentdisclosure. Polishing pads 200 may be used as polishing pad 102 ofFIG. 1. The polishing pad 200 of FIGS. 2A and 2B includes a polishingportion 202 disposed on a backing portion 204. In this illustrativeexample, the backing portion 204 is disposed directly on an adhesive206, which is used to adhere the pad to a rotatable platen 104 forpolishing. In general, the backing portion 204 facilitates compressionof the polishing pad 200 during its use. This is achieved by an elasticmodulus of the polishing portion 202 being different (generally larger)than that of the backing portion 204. Compressibility can effectively beexpressed in terms of an elastic modulus of each portion, where anincreased elastic modulus corresponds to a decreased compressibility.

In general, the backing portion 204 can be provided with a differentcompressibility (or effective elastic modulus) than the polishingportion 202 by one or more of: (1) using a different extent of curingduring manufacturing (e.g., a different intensity of UV radiation), (2)manufacturing the polishing portion 202 with a different structure(e.g., a lattice structure as shown in FIGS. 2A-C, a honeycombstructure, or a structure comprising regularly spaced cylindrical pores)than that of the polishing portion, (3) using a differentphoto-crosslinked polymer for preparing the backing portion 204 than forpreparing the polishing portion 202, and (4) using different additives(or a different amount of additives) during preparation of the backingportion 204 than during preparation of the polishing portion 202. Forinstance, the backing portion 204 shown in FIG. 2A has a latticestructure for increased compressibility. The geometry of this latticecan be tuned to achieve a desired compressibility of the backing portion204.

The polishing pads 200 generally comprise polyurethane, such as aflexible polyurethane or a rigid polyurethane. The pads generally have adensity of between 0.3 and 0.9 g/cm³. In certain embodiments, thedensity of the pad 200 is between 0.5 and 0.9 g/cm³. In certainembodiments, the pads have a preferred density of about 0.7 g/cm³. Insome embodiments, an appropriate porogen may be included with theprecursor at the time the pads 200 are manufactured in order to achievea desired (e.g., decreased) density.

The effective elastic modulus of the pad 200, which is determined by theelastic modulus of the polishing portion 202 and the backing portion204, is generally in a range from about 400 to 600 MPa. As describedabove, the effective elastic modulus (e.g., or the compressibility) ofthe backing portion 204 is generally different than that of thepolishing portion 202. In general, the backing portion 204 is morecompressible (e.g., has a lower elastic modulus) than the polishingportion 202. The elastic modulus of the backing portion 204 may be in arange from about 1 to about 200 MPa. The elastic modulus of thepolishing portion 202 may be in a range from about 400 to about 1200MPa.

As shown in FIG. 2A (top view), the pad generally has a circular orapproximately cylindrical shape. The thickness of the pad 200 may be ina range from about 50 mils to about 400 mils (about 1.27 millimeters toabout 10.16 millimeters), and the diameter from about 20 to 30 inches(about 500 millimeters to about 760 millimeters). The polishing portion202 may have a thickness of about 50 to 155 mils. The backing portion204 may have a thickness of about 15 mil to 150 mils (1 mil=1thousandths of an inch). It should be understood that the polishing pad200 could be any other thickness or diameter as appropriate for a givenpolishing application.

The polishing pads 200 generally have a uniform thickness. A uniformthickness is defined as a thickness that varies by no more than 50%,25%, 20%, 10%, 5%, or less across the radial extent of the pad. In otherwords, the thickness measured near the center of the pad issubstantially the same as the thickness near the edge of the pad.Compared to pads produced by extrusion, foaming, casting, molding orextrusion-based 3D printing, the polishing pads of the presentdisclosure have superior thickness uniformity.

As shown in FIG. 2A (top view), the surface of the polishing portion 202may include patterned grooves. The grooves generally aid in slurrydistribution and waste removal. The illustrative example of FIG. 2A (topview) shows grooves with a “spiderweb” design. However, any otherappropriate groove design is contemplated by the present disclosure. Forexample, the grooves may have a concentric, a concentric and radial, ora hexagonal close-packed design. In general, the grooves are produced bythe processes described herein (e.g., a described with respect to FIG.11). However, grooves may also or alternatively be machined after thepolishing pad is produced according to the present disclosure.

In certain embodiments, such as that shown in FIGS. 2A and 2B, thepolishing pad 200 comprises a continuous, single-body structure, wherethe polishing portion 202 and backing portion 204 are a continuousstructure. Such a continuous single-body structure is in contrast toconventional multilayered polishing pads, which typically have a topsheet that is adhered to a subpad using an intervening adhesive, orbonding layer, disposed between the top sheet and subpad. Suchembodiments obviate the need for this adhesive and thereby providevarious advantages over conventional technology. For example, in commonpolishing processes, slurries are used that contain compounds that mayreact with and weaken the adhesive layer, resulting in possible damageto and failure of the conventional polishing pads. Additionally,polishing pads can be exposed to high temperatures because of heatgenerated during certain polishing steps, and these high temperaturescan weaken the adhesive used to connect the top sheet to the subpad ofconventional polishing pads. This can result in detachment of the padlayers and subsequent pad failure. The continuous single-body polishingpad 200 shown in FIGS. 2A and 2B solves problems of conventionalpolishing pads by eliminating the need for an intermediate adhesivelayer between the polishing portion and the backing portion.

In certain CMP processes, it may be advantageous for the polishingportion 202 and backing portion 204 to comprise different or dissimilarmaterials. For example, it may be beneficial for the polishing portion202 to comprise a polyurethane material, while the backing portion 204comprises a different material such as a polyurethane material with adifferent compressibility, a polystyrene, or a metal. In someembodiments, the backing portion 204 may be prepared in a first vat viaa first vat-based manufacturing process (e.g., in a first additivemanufacturing device), and the completed backing portion 204 may betransferred to a second vat (see step 1116 of FIG. 11) where thepolishing portion 202 is prepared (e.g., in a second additivemanufacturing device). Such a sequential, two-vat process facilitatesefficient production of CMP pad 200.

Referring now to the side view shown in FIG. 2B, the backing portion 204of the polishing pad may be disposed on (e.g., prepared directly on) alayer of platen adhesive 206. The platen adhesive 206 may be, forexample, a thin adhesive layer (e.g., a layer of pressure-sensitiveadhesive) that is operable to adhere the rotating platen of a CMPapparatus. Other adhesives or adhesion processes may also oralternatively be used as appropriate. In certain embodiments, thepolishing pad 200 is manufactured directly on the platen adhesive layer206. For example, the manufacturing process described with respect toFIG. 11 below may be performed on a layer of platen adhesive 206, whicheffectively functions as the build platform. An advantage of thisembodiment is that the pad 200 may be ready to use immediately after thepad 200 is manufactured. Thus, difficult, time-consuming, and costlyprocesses for attaching the pad 200 to the platen adhesive 206 areavoided.

FIG. 2C illustrates a side view of another embodiment of a polishing pad200 according to the present disclosure. In this embodiment, thepolishing portion 202, prepared using the inventive techniques andprocesses described herein, is adhered to a backing portion using anadhesive 208 (e.g., as described above). In other words, in thisembodiment, the polishing portion 202 and backing portion 204 are not acontinuous single-body structure. Instead, the polishing portion 202 issecured to the backing portion 204 by a thin bonding layer 208 (e.g., alayer of pressure-sensitive adhesive or polyurethane plastic layer).Other adhesives may also or alternatively be used as appropriate. Forexample, the adhesive may be a hot-melt adhesive, or the polishingportion and backing portion may be connected by laminating a thin layerof a thermoplastic material between the portions 202, 204. The backingportion 204 may be prepared by the processes described herein, preparedby a separate process, or otherwise appropriately obtained.

In certain implementations of the embodiment shown in FIG. 2C, thebacking portion 204 is fabricated using the processes described herein.However, in other implementations, a conventional additive manufacturingprocess is used to prepare the backing layer such as extrusion-based 3Dprinting. Thus, the backing portion 204 may be used as a build supportfor manufacture of the polishing portion 202. In other embodiments, thepolishing portion 202 may include a material that adheres to the backingportion 204 such that an intervening adhesive layer 208 is not required(as shown in FIGS. 2A and 2B). If the polishing portion 202 comprises apolymeric material that does not adhere to the backing portion 204, anintermediate layer may be disposed on the backing portion 204 tofacilitate attachment of the polishing portion 202 without requiring anintervening adhesive layer 208.

In various embodiments, the pad 200 includes an aperture therein, suchthat an end-point detection element can be placed in the aperture. Anysuitable end-point detection element may be used (e.g., any sensor todetect when a polishing process is complete). Various shapes andconfigurations for the end-point detection element can be designed usingthe unique pad manufacturing processes described herein. By forming theaperture using the processes of the present disclosure (e.g., asdescribed with respect to FIG. 11 below), less material is wasted thanwhen conventional pad manufacturing processes are used, which typicallyrequire a section of the pad to be removed and discarded to form theaperture.

Porous Polishing Surface

FIG. 3 depicts a microscopic view of a polishing surface 300 of apolishing portion 202 that includes pores 302, 304 of different sizes,shapes, and/or orientations. As shown in FIG. 3, in some embodiments,the polishing surface 300 may include pores 302, 304 with a bimodal poresize distribution. In other words, a first set of pores 302 may have amean particle size that is smaller than that of a second set of pores304. For example, a first set of pores 302 may have a mean particle sizeof about 5 to about 200 microns, and a second set of pores 304 may havea mean pore diameter of about 50 to 500 microns. In this embodiment, thefirst set of pores 302 may be produced using a porogen (e.g., a porosityforming agent or “pore filler”), and the second set of pores 304 may bepatterned using the vat-based manufacturing process (e.g., continuousliquid interphase production, e.g., as described with respect to FIG.11). Alternatively, the first set of pores 302 and the second set ofpores 304 may be generated using porogens that generate pores ofdifferent sizes (e.g., porogens with different diameters and/or thatexpand to different sizes during preparation of the polishing surface300). One or more additional sets of pores (not shown for clarity andconciseness) may also be prepared using the processes described hereinand/or one or more additional porogens.

Example porogens suitable for the polishing pads 102 described hereininclude spherical or nearly-spherical, hollow particles. The porogensmay have a diameter of about 5 to about 500 microns. The porogens may bedistributed evenly throughout the pad or located in one or more regionsof the pad. In some embodiments, bimodally distributed pores are locatedonly near the polishing surface 300 illustrated in FIG. 3. For example,smaller pores 302 may only be required near the polishing surface 300where they increase the contact area between the polishing pad and asurface being polished. Additionally, the larger pores 304, which mayalso be located at or near the polishing surface 300, are believed toimprove slurry 110 retention and transport, thereby increasing thecontact area between the slurry 110 and substrate 106 for improvedpolishing (see FIG. 1 for reference). The precursor mixture used toprepare a polishing pad 102 may include porogens at a mass percentage ofabout 1% to about 30% (by weight). In certain embodiments, the precursormixture used to prepare a polishing pad 102 includes 30% (by weight) ofthe porogen. In some embodiments, precursor mixture used to prepare apolishing pad 102 includes from 1% to 5% (by weight) of the porogen. Incertain embodiments, the porogen has a similar density to that of theprecursor material used to prepare the polishing pad, therebyfacilitating even distribution of the porogen in each layer of the padduring its manufacture. Examples of porogens include Expancel DU powderssuch as 551 DU 40, 461 DU 20, 461 DU 40, 051 DU 40, 031 DU 40, and 053DU 40.

In another embodiment, the polishing pad 102 comprises a plurality ofelongated pores 304 having an aspect ratio of about 2:1 or greater. Theelongated pores 304 are not the result of porogen incorporation but arerather formed from the vat-based manufacturing process. In thisembodiment, about 10% or more of the pores 302, 304 have an aspect ratioof about 2:1 or greater (e.g., about 3:1 or greater, about 5:1 orgreater, about 10:1 or greater, or about 20:1 or greater). Desirably,about 20% or more (e.g., about 30% or more, about 40% or more, or about50% or more) of the pores 302, 304 have an aspect ratio of about 2:1 orgreater (e.g., about 3:1 or greater, about 5:1 or greater, about 10:1 orgreater, or about 20:1 or greater). Preferably, about 60% or more (e.g.,about 70% or more, about 80% or more, or about 90% or more) of the pores302, 304 have an aspect ratio of about 2:1 or greater (e.g., about 3:1or greater, about 5:1 or greater, about 10:1 or greater, or about 20:1or greater).

The elongated pores 304 may be oriented in a direction that is coplanarwith the polishing surface 300 of the polishing pad 102 or perpendicularto the surface 300. When the elongated pores 304 are oriented in adirection that is perpendicular to the surface 300, the pores 304 mayspan the thickness of the polishing portion (e.g., portion 202 of FIGS.2A-2C) of the pad 102, or some percentage of the thickness of thepolishing portion. That is, the pores 304 may create an opening from thepolishing surface 300 of the polishing portion to the back surface ofthe polishing portion.

In another embodiment, the pores 302, 304 may result in a polishingsurface 300 with uniformly sized (and/or spaced) asperities. In variousembodiments, a property (e.g., asperity size or density) may beconsidered uniform, if that property when measured in two or moresimilarly sized regions of the polishing pad differ by no more than 50%,25%, 20%, 10%, 5%, or less. Asperities of uniform height (e.g., size)and density may be produced using the methods described herein toimprove polishing performance. In conventional polishing pads,asperities are generated by conditioning the surface of the pad,typically by contacting the pad with a diamond conditioner. The asperitysize distribution depends on both the properties of the pad and theconditioning process used. Thus, conventional pads typically have a wide(e.g., and non-uniform) distribution of asperity sizes. In someembodiments, similar asperities are prepared using a vat-basedmanufacturing process as described herein without necessarily requiringaddition of a porogen. Thus, the polishing pads 102 of the presentdisclosure can be designed to have a very uniform distribution ofasperity size (e.g., height) because the asperities formed do notnecessarily rely on conditioning steps like those required by polishingpads made by conventional methods. In some embodiments, the uniformlysized asperities of the polishing surfaces facilitate improvedpolishing, particularly for certain substrates. Moreover, the pads 102of the present disclosure can be prepared with the same asperitycharacteristics between batches, facilitating improved pad-to-padreproducibility. This is not possible for conventional pads produced byfoaming, casting, or molding processes.

In certain embodiments, the pads 102 may include chemical additives(e.g., embedded or encapsulated within at least the polishing portion)for enhanced polishing performance. The additives may be any suitablematerial that would have an advantageous effect on the polishing of agiven substrate 106. For example, one or more of dishing control agents,rate enhancing agents, or film forming agents may be encapsulated andintegrated into the pad 102 using the processes described herein. As thepad wears during normal use, encapsulated additives are released andcontact both the substrate 106 and polishing slurry 110. In this way,additional slurry components, which may otherwise be too reactive orunstable when added directly to the slurry 100, may be incorporated intothe pad 102 itself. These pad-embedded slurry components would thus onlybe exposed to the slurry 100 for a brief time, reducing or eliminatingunwanted reactions between the slurry components.

Spatial variation of Polishing Pad Compressibility

FIG. 4 illustrates a polishing pad 102 of the present disclosure beingused to polish a wafer 106 held in a wafer holder by a retaining ring(e.g., attached to the head 108 of FIG. 1). As described herein,polishing properties can be tuned through spatial control of thecompressibility (e.g., via the effective elastic modulus) of the backingportion 204 of the pad 102. Compressibility of the backing portion 204can be controlled, for example, by (1) controlling the extent of curingduring manufacturing (e.g., a different intensity of UV radiation), (2)manufacturing the backing portion 204 with an appropriate structure(e.g., a lattice structure as shown in FIGS. 2A-C, e.g., a honeycombstructure or a structure comprising regularly spaced cylindrical pores)corresponding to a desired compressibility, (3) using an appropriatephoto-crosslinkable polymer (e.g., a more flexible polyurethane) forpreparing the backing portion 204, and (4) using one or more appropriateadditives (or a different amount of additives) during preparation of thebacking portion 204.

For conventional polishing pads, the polishing rate is non-uniform nearthe edge of the wafer (e.g., near the retaining ring used to hold thewafer to the carrier head). This non-uniform polishing at the edge ofthe wafer is sometimes referred to as an “edge effect” or “edgeexclusion.” Certain embodiments of the polishing pads described hereinreduce or eliminate this problem.

The polishing portion 202 (or the entirety of the polishing pad) may beformed in a continuous layer-by-layer fashion (e.g., as described withrespect to FIG. 11). This allows continuous changes in pore structureand pore size to be formed according to precise specifications using thevat-based manufacturing process. This precise control of pore geometryin turn facilitates improved control of the density, hardness, and otherphysical characteristics of the polishing pad 102. In general, the size,shape and distribution of pores (see FIG. 3) may be tightly controlledusing the processes described herein. Pores may be uniform in ahorizontal plane relative to the polishing surface but may vary in avertical plane. For example, there may be smaller, substantiallyspherical pores with a low void volume in a horizonal plane at adistance away from the polishing surface. The pore size, shape and voidvolume can then change as the distance of a horizontal plane approachesthe polishing surface. The change can be gradual or a step change.

Additionally, the size, shape and distribution of the pores can bevaried along the horizontal plane to give regions of varyingcompressibility on the pad 102, as shown in FIG. 4. For example, poresof differing sizes, structures, and/or densities can be formed in eitheror both of the polishing portion 202 and the backing portion 204 suchthat regions of the polishing pad 102 each have differentcompressibility. For example, a region of the pad 102 with pores of afirst shape (e.g., a cylindrical shape) will have a differentcompressibility than a region with pores of a different second shape(e.g., a polygonal shape such as a honeycomb). Additionally, the size ofthe pores and the volume of the pores (e.g., the void volume of the pad102) can be modulated to control the compressibility of both thepolishing pad as a whole and regions of the polishing pad 102. Forexample, the pad 102 may be constructed to have a more compressibleregion around the edge of the pad, while the region near the center ofthe pad 102 is less compressible. This variation of pad compressibilitymay improve the polishing characteristics to reduce edge erosion andimprove planarization efficiency for certain substrates 106. Thephysical characteristics of the pad 102 (e.g., its hardness andcompressibility) can thus be precisely designed to match the slurries110 used during polishing and the substrates 106 being polished.

Still referring to FIG. 4, the structure of the backing portion 204 inparticular may be tuned to provide different regions (e.g., areas) ofthe pad that are suited for different polishing needs. For example, asshown in FIG. 4, the edge of a wafer 106 being polished (i.e., theregion near the retaining ring) may experience a greater pressure thanthe center of the wafer 106 via a downward force (DF) 402 applied to thewafer 106 during polishing. A conventional pad would typically“overpolish” this edge portion of the wafer 106. The polishing pad 102shown in FIG. 4, however, includes a backing portion 204 that is morecompressible in the region where the retaining ring edge of the wafer106 contacts the pad 102, thereby reducing or eliminating“overpolishing” and facilitating more uniform polishing over the entirewafer 106 surface.

As described above, the backing portion 204 can be provided with adifferent compressibility than the polishing portion by one or more of:(1) using a different extent of curing during manufacturing (e.g., adifferent intensity of UV radiation), (2) manufacturing the polishingportion 204 with a different structure (e.g., a honeycomb structure or astructure comprising regularly spaced cylindrical pores) than that ofthe polishing portion 202, (3) using a different photo-crosslinkablepolymer for preparing the backing portion 204 than for preparing thepolishing portion 202, and (4) using different additives (or a differentamount of additives) during preparation of the backing portion 204 thanduring preparation of the polishing portion 202.

It should be understood that FIG. 4 presents one example embodiment ofhow the compressibility of the polishing pad 102 can be varied spatiallyto improve polishing performance. The present disclosure contemplatespolishing pads 102 with any appropriate compressibility profile for agiven application. In general, during a polishing process, the wafer 106may be contacted to the appropriate region(s) of the pad 102 based onthe known compressibility profile of the pad 102.

Example CMP Pad Designs

The structures of CMP pads 102 prepared via the vat-based manufacturingprocesses described in this disclosure may facilitate improvedplanarization and improved pad 102 lifetime. Examples of pad designs areshown in FIGS. 5A-5B and 6A-6D, which are described below. Certain paddesigns described herein may only be achieved using the unique vat-basedmanufacturing processes described herein (see, e.g., FIG. 11). While insome embodiments, the unique preparation processes described in thisdisclosure may facilitate the preparation of these pad designs, itshould be understood that in some embodiments certain pad designsdescribed herein may be achieved using any appropriate fabricationprocess or combination of processes (e.g., molding, casting,deposition-based additive manufacturing, etc.).

FIGS. 5A and 5B illustrate a design of an example pad 500. Pad 500 is anexample embodiment of the pad 102 of FIG. 1. FIG. 5A shows a topperspective view of the polishing pad 500, and FIG. 5B shows aperspective view of a cross-section showing the internal structure ofthe polishing pad 500. As illustrated in FIGS. 5A and 5B, the pad 500includes grooves 502, top-side holes 504, and outlet holes 506. Asillustrated in the cross-section image of FIG. 5B, top-side holes 504extend partially into the surface of the pad 500 and are coupled tochannels 508, which are embedded beneath the surface of the pad 500. Thedesign of pad 500 generally facilitates improved transport of freshslurry 110 to a surface being planarized by the pad 500. The grooves 502facilitate transport of fresh slurry 110 (i.e., slurry 110 which stillcontains active components which aid in the CMP process) toward thesurface of a wafer 106 being planarized (see also FIG. 1). Meanwhile,expended slurry 110 (i.e., slurry 110 in which the active componentshave largely already been consumed during the planarization process)and/or polishing byproducts may be transported away from the surface ofthe wafer 106 via the holes 504, 506 and channels 508 (e.g., when thepad 500 is rotated, see also FIG. 1). As such, the concentration offresh slurry 110 near the surface being planarized is increased anddilution of fresh slurry 110 by expended slurry 110 is decreased.

The grooves 502 may be concentric as shown in the example of FIGS. 5Aand 5B or any other appropriate pattern (e.g., concentric, concentricand radial design, or a hexagonal close-packed design). The grooves 502may have any appropriate pitch and width. The pad 500 may include anyappropriate number of grooves 502. For example, the number of groovescan be increased or decreased as needed to be able to hold more or lessfresh slurry 110 during polishing.

The diameter of the top-side holes 504 may vary from about ten mils toabout 400 mils (1 mil=1 thousandths of an inch). In general, largertop-side holes 504 may facilitate increased transport of expended slurry110 away from a surface being polished. In some embodiments, if largertop-side holes 504 are present in the pad 500, the number of holes 504may be decreased to facilitate appropriate spacing and structuralproperties of the pad 500. The number of radial lines of holes 504 canvary from one to about 128. In general, the presence of more radiallines of holes 504 facilitates increased slurry 110 transport throughthe holes 504. Generally, the number of holes 504 per radial line canvary. The example of FIG. 5A includes thirteen top-side holes per radialline. However, more or fewer holes 504 may be present in each radialline.

While the examples of FIGS. 5A and 5B show circular top-side holes 504,it should be understood that the holes 504 may have any shape. Forexample, the top-side holes 504 (and the outlet holes 508) may have asquare, rectangular, oval, star, triangular, hexagonal, semi-circular,or conical shape. A hole 504 with a conical shape has a diameter thatdecreases with depth into the surface of the pad 500. The differentshapes of holes 504 may facilitate different slurry 110 transportproperties which may be desirable for certain applications. In someembodiments, the shape of the holes 504 may only be achieved using thevat-based manufacturing approaches described in this disclosure (see,e.g., FIG. 11).

The channels 508 are generally shaped and positioned to receive slurryvia the top-side holes 504 and allow transport of the slurry 110 out ofthe pad 500 via the outlet holes 506. As such, the channels 508 andoutlet holes 506 may have any appropriate configuration for facilitatingthis transport or slurry 110. The example of FIG. 5B illustrates examplechannels 508 that extent radially from the center of the pad 500 to acorresponding outlet hole 506. However, any other appropriate channel508 and outlet hole 506 configuration is possible. For instance, in someembodiments, the top-side holes 504 may have a different configurationthan the circular pattern illustrated in FIGS. 5A and 5B. For instance,the top-side holes 504 may be distributed in a spiral shape, in a squareshape, in straight lines, in a box-like pattern, at diagonal angles, andthe like. The channels 508 and outlet holes 506 have an appropriatecomplementary pattern or layout to facilitate transport of slurry 110which is received via the holes 504, out of the outlet holes 506 duringrotation of the pad 500.

The diameter of the pad 500 can vary based on intended use. For example,the diameter of the pad 500 may range from about eight inches to about46 inches. The thickness of the pad 500 can also vary. For example, thethickness of the pad 500 may range from about 60 mils to about 600 mils.In some embodiments, the thickness of the pad 500 is about 400 mils. Thesize of the top-side holes 504 and outlet holes 506 may be adjusted toaccommodate slurry 110 transport in pads 500 of different thickness.

In some embodiments, the vat-based manufacturing processes described inthis disclosure (see FIG. 11) uniquely facilitate fabrication of theexample polishing pad 500. For example, the polishing pad 500 withtop-side holes 504 of the appropriate depth and dimensions cannot beprepared via casting or molding. Reliable generation of both holes 504,506 and the channels 508 of an appropriate size and configuration maynot be possible via drilling because of the limitations of availabledrilling technology. For example, it may not be feasible toretroactively drill the holes 504, 506 and channels 508 in aconventional polishing pad such that the holes 504, 506 and channels 508are appropriately aligned for slurry 110 transport, as in the examplepad 500 of FIGS. 5A and 5B. Moreover, an extrusion-based additivemanufacturing approach may not be able to reliably create the pad 500with holes 504, 506 and channels 508 because internal supports may beneeded for each channel 508 and outlet hole 506. Such supports mayhinder slurry 110 transport in the pad.

FIGS. 6A-6D illustrate an example pad 600. Pad 600 is an exampleembodiment of the pad 102 of FIG. 1. As described further below, the pad600 facilitates the transport of expended slurry 110 and/ordebris/byproducts formed during the polishing process away from asurface being polished. More particularly, pad 600 includes top grooves606 for retaining slurry 110 near the surface being polished as well astop-side holes 608, which are coupled via channels 612 to outlet holes614, for transporting expended slurry 110 away from the surface beingpolished. FIG. 6A shows the pad 600 with a top potion 602 and a backingportion 604. While the top portion 602 and backing portion 604 aredescribed separately with respect to FIGS. 6B and 6C below, it should beunderstood, that the pad 600 may be a single-body, continuous structure.For example, the pad 600 may be prepared using a method of additivemanufacture (e.g., as described with respect to FIG. 11 below) such thatthe top portion 602 and backing portion 604 form one single-bodystructure. In other embodiments, the top portion 602 and backing portion604 may be prepared separately (e.g., using any appropriate method) andcombined to form the pad 600.

The diameter of the pad 600 can vary based on intended use. For example,the diameter of the pad 600 may range from about eight inches to about46 inches. The thickness of the pad 600 can also vary. For example, thethickness of the pad 600 may range from about 50 mils to about 300 mils.For example, the thickness of the top portion 602 may range from about30 mils to about 160 mils, and the thickness of the backing portion 604may range from about 20 mils to about 100 mils.

As shown in FIG. 6B, the top portion 602 includes grooves 606 andtop-side holes 608. The example of FIG. 6B includes concentric grooves606. However, it should be understood that the grooves 606 may have anyappropriate pattern (e.g., a concentric, concentric and radial design,or hexagonal close-packed design). The grooves 606 may have anyappropriate pitch and width. The top portion 602 may include anyappropriate number of grooves 606. For example, the number of grooves606 may be increased or decreased as needed to be able to hold more orless fresh slurry 110 during polishing.

The top-side holes 608 may be located on the bottom of the grooves 606and facilitate the evacuation and/or drainage of expended slurry 110and/or any byproducts of polishing away from the surface being polished.In other embodiments, the top-side holes 608 may be located on the topportion 602. For instance, the top-side holes 608 may be positioned onthe surface of the top portion 602 (e.g., similarly to the top-sideholes 504 of pad 500 described above with respect to FIGS. 5A and 5B).The diameter of the top-side holes 608 may vary from about five mils toabout 500 mils. The size of the top-side holes 608 is generally selectedto balance between the benefits of transporting slurry 110 away from apolished surface when the holes 608 are larger and the ability to limitthe amount of slurry 110 consumed when holes 608 are smaller.

While the example of FIG. 6B shows rectangular top-side holes 608, itshould be understood that the holes 608 may have any shape. For example,the top-side holes 608 may have a square, circular, oval, star,triangular, hexagonal, semi-circular, or conical shape. In someembodiments, the shape of the holes 608 may only be achieved using thevat-based additive manufacturing approaches described in this disclosure(see, e.g., FIG. 11). The top-side portion 602 may include anywhere fromone to 100,000 top-side holes 608, and the top-side holes 608 may bedistributed according to any appropriate pattern.

As shown in FIG. 6C, the backing portion 604 includes concentricchannels 610 and radial channels 612, which couple the top-holes 608 tothe outlet holes 614 in order to facilitate the transport of expendedslurry 110 and/or byproducts of planarization away from the surfacebeing polished. The backing portion 604 may be the same or a differentmaterial to that of the top portion 602. In some embodiments, thebacking portion 604 is a relatively soft material compared to the topportion 602. In some embodiments, the backing portion 604 has a latticestructure (e.g., similar to the backing portion 204 of FIGS. 2A-2C). Thesize of the channels 610, 612 may range from about ten mils to about 90mils. The channels 610, 612 and the outlet holes 614 may have any shape.For example, the channels 610, 612 and the outlet holes 614 may have asquare, rectangular, circular, oval, star, triangular, hexagonal,semi-circular, or conical shape.

In some embodiments, the radial channels 612 may be at an angle suchthat the channel 612 is at a higher elevation near the center of thebacking portion 604 and at a lower elevation near the edge of thebacking portion 604. This angled structure may further facilitate thetransport of expended slurry 110 and/or polishing byproducts through theradial channels 612 and out of the outlet holes 614. FIG. 6D illustratesa cross section of a portion 620 of an example pad 600 with such anangled channel 612. The channel 612 transports slurry 110 from left toright (i.e., from the center of the pad 600 to the outlet hole 614 ofthe channel 612). The channel 612 may be at an angle 622 of up to about15 degrees.

CMP Pads with Buried Grooves

As described above, one objective of chemical mechanical planarizationis to achieve a high polishing uniformity. If different areas on thesubstrate 106 are polished at different rates, then it is possible forsome areas of the substrate 106 to have too much material removed(“overpolishing”) or too little material removed (“underpolishing”).Conventional CMP pads may include a limited range of groove designs toimprove CMP performance to some extent. However, after use, thesegrooves may effectively be removed from the surface of conventionalpolishing pads. Once the grooves are gone, CMP performance is generallydiminished and a new polishing pad is used, resulting in down-timeduring which wafers cannot be processed (e.g., using a system such asthe one described above with respect to FIG. 1). There exists a need forCMP pads, and methods of their manufacture and use, that can provideimproved polishing uniformity and increased polishing pad lifetime.

This disclosure not only recognizes problems of previous CMP pads,including those described above, but also a solution to these problems.In some embodiments, the polishing pads 102 described in this disclosureprovide increased polishing pad lifetimes so that the polishing pads 102may be used for longer periods of time without requiring processes to bestopped frequently to replace the polishing pad 102. In variousembodiments, the CMP pads 102 may include buried grooves and/or embeddedchannels. The buried grooves generally facilitate increased polishingpad lifetimes (see, e.g., FIGS. 7A-7C), while the channels (see FIGS.8A-E) may facilitate, amongst other things, improved performance duringuse (e.g., byproducts and/or debris generated during CMP may be removedfrom the surface and/or fresh slurry 110 may be replenished near thesurface being planarized). The buried grooves and/or grooves may also oralternatively facilitate more straightforward polishing pad preparation(e.g., by providing a flow path to remove residual chemicals left behindafter the fabrication process—see, e.g., step 1120 of FIG. 11 andcorresponding description below). In some embodiments, the polishingpads 102 include reservoirs to collect slurry 110 and/or move residualmaterials (e.g., debris generated during polishing, slurry byproducts,etc.) away from the surface being polished (see, e.g., FIGS. 9 and10A,B). The present disclosure further recognizes that a polishing pad102 with improved chemical and mechanical properties, such as thepolishing pads 102 with buried grooves and/or channels described below,may particularly be efficiently produced using a vat-based manufacturingprocess.

This disclosure further recognizes that the performance of CMP may beimproved when the volume of exposed grooves (i.e., the combined volumeof all exposed grooves on the surface of a polishing pad) is within apredetermined range. The predetermined range may be measured relative toan initial volume of all grooves prior to use of a polishing pad 102 forCMP. For example, in conventional polishing pads, only about 80% of agroove height (and thus of groove volume) is useable before CMPperformance degrades precipitously. For instance, for certain CMPprocesses it may be desirable to have a groove volume that is greaterthan about 20% of an initial groove volume. In some embodiments, thegroove volume of the polishing pad 102 is maintained in a range fromabout 90% to about 25% of the initial groove volume. Maintaining groovevolume within a predetermined range, such as one of those describedabove, may allow CMP to be performed at a lower slurry 110 flow rate(i.e., the system 100 may require less slurry 110 to be introducedduring the CMP process), thereby reducing costs.

FIG. 7A is a diagram illustrating a cross-sectional side-view of aportion 700 of a polishing pad 102 at an initial time (t₀) and at twoother time points (t₁ and t₂) following use for CMP. The polishing padportion 700 includes exposed grooves 702a-c and buried grooves 702d. Asan example, the grooves 702a-d may have a width in a range of about 5mils (1 mil=1 thousandths of an inch) to about 500 mils (e.g., or fromabout 10 mils to about 50 mils) and a height in a range of about 5 milsto about 500 mils (e.g., from about 10 mils to about 50 mils). However,the grooves 702a-d may have any other height and width. The grooves702a-d are generally offset vertically (e.g., are buried at differentdepths) as shown in the example of FIG. 7A such that during the use ofpolishing pad 102, the volume (V) of the exposed grooves 702a-c isapproximately constant, or maintained within a predetermined range, nearits initial value (V₀). For example, at time t₁, after CMP is performedfor a period of time, a top layer 704 of the polishing pad 700 isremoved through conditioning and general wear. However, because thecenter buried groove 702d from time to is now exposed as groove 702b attime ti, the volume of the exposed grooves remains approximatelyconstant, or within a predetermined range, near V₀. In some embodiments,the grove volume is maintained with less than an 80% variation from V₀.In other embodiments, the groove volume is maintained with less than a25% variation from V₀. Similarly, at time t₃, following further CMP, theleft and right-most buried grooves 702d become exposed grooves 702a and702d after layer 706 is removed, resulting in a consistent groove volumeat or within a predetermined range near V₀.

FIG. 7B is a diagram illustrating a cross-sectional side-view of anotherembodiment of a portion 710 polishing pad 102. Polishing pad portion 710includes buried grooves 712d with a variable height. Grooves 712a-d mayhave a similar size to that of grooves 702a-d described above. Thisdesign facilitates the gradual opening of the grooves 712d during CMP.This may decrease the amount of pad debris that is introduced during CMPand further improve CMP results. FIG. 7B illustrates a cross-sectionalside-view of a portion 710 of polishing pad 102 at an initial time (t₀)and at two other time points (t₁ and t₂) following CMP. Polishing padportion 710 includes exposed grooves 712a-c and buried grooves 712d. Thegrooves 712a-d are generally offset vertically (e.g., are buried atdifferent depths) as shown in the example of FIG. 7B such that duringthe use of polishing pad 710, the volume (V) of the exposed grooves712a-c is approximately constant, or maintained within a predeterminedrange, near its initial value (V₀). For example, at time ti, after CMPis performed for a period of time, a top layer 714 of the pad portion710 is removed. However, because the center buried groove 712d from timeto is now exposed as groove 712b at time ti, the volume (V) of theexposed grooves remains approximately constant, or within apredetermined range, near V₀. Similarly, at time t₃, following furtherCMP, the left and right-most buried grooves 712d are now exposed grooves712a and 712d after layer 716 is removed, resulting in a consistentgroove volume (V) at or within a predetermined range near V₀.

While the examples of FIG. 7A and 7B show only two to three layers ofburied grooves 702d, 712d, it should be understood that there may bemany more layers of buried grooves 702d, 712d. For example, in someembodiments, there are up to or greater than 30 layers of buried grooves702d, 712d. The number of layers of buried grooves 702d, 712d isgenerally only limited by the thickness of the polishing pad 102. Vatbased manufacturing facilitates the preparation of relatively thickpolishing pads 102 with many layers of buried grooves 702d, 712d.Accordingly, the polishing pads 102 may be used continuously (e.g.,without conditioning) for long periods of time while maintaining anearly constant groove volume at or within a predetermined range nearV₀.

Another benefit of the buried grooves 702d, 712d of the examplepolishing pads 102 is to provide reinforcement and support to theoverall structure of the polishing pads 102, thereby facilitating theburied groove designs illustrated in FIGS. 7A and 7B. Accordingly,buried grooves 702d, 712d may be formed without significantlysacrificing the mechanical properties (e.g., rigidity) of the overallstructures of polishing pads 102. For this additional reason, polishingpad lifetimes can be extended compared to those of conventionalpolishing pads.

Very deep grooves generally cannot be used because very large groovevolumes can lead to “slurry starving,” or conditions where so muchslurry is lost to the volume of the grooves that sufficient slurry isnot available at the surface of the polishing pad for CMP. When groovesare too shallow (e.g., less than the newly recognized 20% of the initialvolume level, results of CMP may begin to degrade (e.g., because ofoverheating). This can result in poor polishing uniformity (e.g.,increased within-wafer non-uniformity (WIWNU) and/or increased defectdensity).

FIG. 7C is a diagram illustrating another embodiment of a portion 720 ofa polishing pad 102. Polishing pad portion 720 includes smaller grooveswith a much smaller pitch (i.e., the center-to-center distance betweenadjacent grooves) than the grooves 702a-d of polishing pad portion 700described above, for example. Polishing pad portion 720 generally has asmaller groove volume than do example polishing pad portions 700, 710described above with respect to FIGS. 7A and 7B. For instance, thegrooves of polishing pad portion 720 may be two to ten times (or more)smaller (i.e., in terms of length and width) than the grooves 702a-ddescribed above with respect to polishing pad portion 700 of FIG. 7A. Asmaller groove volume may allow the pad portion 720 to providehigh-performance CMP polishing while consuming less slurry material thanis required using either conventional polishing pads or the polishingpad portions 700, 710 described above. Generally, using very smallgrooves like those of polishing pad potion 720 may cause the polishingpad portion 720 to degrade relatively rapidly such that conventionalpolishing pads with small grooves would be expended rapidly (i.e.,because the grooves would be “lost” after only a brief use). However, byusing multiple layers of buried grooves, the small grooves of polishingpad portion 720 can be used with acceptable, or even improved, polishingpad lifetime.

CMP Pads with Channels

FIGS. 8A-8E illustrate various embodiments of polishing pads 102 whichinclude channels. In some cases, the channels provide a flow pathbetween buried grooves (see FIGS. 8A-8E), between buried grooves and thetop surface of the polishing pad (see FIGS. 8A-8D), and/or betweenburied grooves and another edge or surface of the polishing pad 102 (seeFIGS. 8D and 8E). These flow paths may facilitate the removal of slurry110, particulate debris that forms during polishing, and/or chemicalbyproducts formed during CMP away from the surface of a wafer 106 thatis being polished, thereby improving the quality of surfaces planarizedusing these polishing pads 102.

FIGS. 8A and 8B illustrate portions 800 and 810 of polishing pads 102which include grooves 802, vertical channels 804, and horizontalchannels 806. For example, a pad portion 800, 810 may be a portion ofthe polishing layer 204 of the polishing pad 200 described above withrespect to FIGS. 2A-2C. The channels 804, 806 provide a flow path forresidual fluid (e.g., residual polymer precursor remaining in thegrooves 802 following vat-based processing) to drain from the polishingpad portions 800, 810. For example, following their manufacture andbefore their use, the polishing pad portions 800, 810 may be rinsed(e.g., see step 1120 of FIG. 11, described below), and residual fluids,which would otherwise be trapped in the grooves 802 (i.e., if channels804, 806 were not present), may be drained from the grooves 802. Thepolishing pad portions 800, 810 can then be used for CMP (e.g., usingsystem 100 described above with respect to FIG. 1) without potentiallycontaminating the surface of a wafer 106 or any other surface beingplanarized with the residual precursor material.

FIGS. 8C and 8D illustrate polishing pad portions 820, 830 which havealternative groove and channel designs. Pad portions 820, 830 may be aportion of the polishing layer 202 of the CMP pad 200 described abovewith respect to FIGS. 2A-2C. These groove and channel designs, forexample, may be suited for both providing flow paths for the removal ofresidual precursor material following polishing pad fabrication anddirecting expended slurry 110 away from the surface of the polishing padportions 820, 830. As described above, the expended slurry 110 generallycorresponds to slurry 110 in which active components have alreadyreacted or have otherwise been consumed. For example, polishing padportion 820 of FIG. 8C has angled channels 822 connecting grooves 802 tothe vertical channels 804. The angled channels 822 may facilitatedrainage of precursor fluid from the grooves 802 (e.g., when polishingpad 820 is placed top-side down) and may facilitate the flow of expendedslurry and other debris generated during CMP away from the surface ofthe polishing pad portion 820.

Polishing pad portion 830 shown in FIG. 8D includes grooves 802connected via horizontal channels 806 to vertical channels 804 (e.g.,similar to polishing pads portions 800 and 810 described above).Polishing pad portion 830 also includes a horizontal drain channel 832,which facilitates the drainage of slurry 110 out of the polishing padportion 830 (e.g., out of an edge of the pad—see, e.g., pads 500 and 600described above with respect to FIGS. 5A-6D). In some cases, the grooves802 and channels 804, 806 may be filled with slurry 110, and this slurry110 may be released during CMP to replenish active components near thesurface being planarized.

FIG. 8E illustrates a portion 840 of a polishing pad 102 prepared with avertical drain channel 842 which extends from the bottom of thepolishing pad 102 to the top-most buried grooves 802. The design of thepolishing pad portion 840 facilitates the removal of residual materialfrom the grooves 802 after the polishing pad 840 is prepared (see, e.g.,step 1120 of FIG. 11, described below). For instance, liquid precursormaterial from the vat-based manufacturing process used to manufacturepolishing pad 102 with the design of portion 840 may be drained viachannels 842. If is not desirable to retain these channels during use ofthe polishing pad portion 840. The channels 842 may be backfilled with asecond material 852. The second material 852 may be different than thepad material 840, or the second material 852 may be the same as the padmaterial 840, as illustrated in FIG. 8E. In some embodiments, the secondmaterial 852 may be slurry 110 or any other material which, whenreleased during use of the polishing pad 102 with portion 840, promotesimproved CMP of a wafer 106 or other material being planarized.

CMP Pads with Slurry Reservoirs

During use of conventional polishing pads, a gradient develops in theconcentration of active components in the slurry 110, for example, fromthe leading to the trailing edge of a wafer 106 that is beingplanarized. In other words, the concentration of active slurrycomponents may be decreased near the surface being planarized. This canlimit the performance of these conventional polishing pads. Variousembodiments of the polishing pads 102 described in this disclosureinclude slurry reservoirs which can aid in overcoming challenges andperformance limitations associated with decreased slurry 110concentration near the surface being planarized. The slurry reservoirsgenerally provide a source of slurry active ingredients near the surfaceof the polishing pads 102 such that the active materials are rapidlyreplenished after they are consumed during CMP. As an example, any ofthe polishing pads 102 (i.e., polishing pad portions 800, 810, 820, 830,840) described above with respect to FIGS. 8A-8E may be loaded withslurry 110 (i.e., the grooves and channels of the polishing pads may befilled with slurry 110) to prevent or limit the development of slurryactive ingredient concentration gradients during CMP. Further examplesof polishing pads 102 configured with slurry reservoirs for improved CMPare described below with respect to FIGS. 9 and 10A,B.

FIG. 9 illustrates a polishing pad portion 900 (i.e., a portion 900 ofan example polishing pad 102) which includes both relatively smallgrooves 902 and larger slurry grooves 904 which may act as slurryreservoirs. The smaller grooves 902 may enhance local slurry 110distribution during CMP. The larger grooves 904 may facilitate rapiddistribution of slurry 110 along the entire surface (e.g., globallyrather than locally) of the wafer 106. The combination of both smallgrooves 902 and relatively large slurry reservoirs 904 may reduce theconcentration gradient of active slurry 110 near the wafer surface,thereby resulting in improved CMP. The grooves 904 may be similarlysized to those illustrated in FIG. 7A (described above) or may be larger(e.g., one and a half times, or more, of the size of grooves 702a-d ofpolishing pad 700 illustrated in FIG. 7A). The larger reservoir grooves904 may provide a path for slurry byproducts to be carried away from thesurface of the polishing pad 900. This may help maintain a desirableslurry 110 distribution at the surface of the polishing pad 900 whereCMP occurs. For example, the small grooves 902 may have a hexagonalpattern or any other appropriate pattern. While the example of FIG. 9illustrates small grooves 902 parallel to the large grooves 904, otherdesigns are contemplated (e.g., with small grooves 902 perpendicular tothe large grooves 904). The exemplary design of FIG. 9 is just oneexample of many related designs (i.e., with both small grooves 902 andlarger grooves 904) contemplated by this disclosure.

FIG. 10A illustrates an example polishing pad portion 1000 (i.e., aportion 1000 of an example polishing pad 102) with horizontal channels1006 connecting buried grooves 1002 to vertical channels 1004. Thechannels 1004, 1006 generally facilitate the flow of slurry 110 into thegrooves 1002. Once buried grooves 1002 are filled with slurry 110, thepolishing pad 1000 may be less compressible, and the resultingslurry-filled polishing pad 1000 is “stiffer,” resulting in improvedplanarization efficiency compared to that of a conventional polishingpad. FIG. 10B illustrates another polishing pad portion 1020 (i.e., aportion 1020 of an example polishing pad 102) which includes grooves1022 which are fluidically connected vertically via channels 1024. Theexample polishing pads 1000, 1020 illustrated in FIGS. 10A and 10Bgenerally provide an increased volume for holding slurry 110. In someembodiments, the channels 1004, 1006, 1024 may be narrow to prevent orreduce dilution of slurry 110 within the channels 1004, 1006, 1024 whenthe pad 1000 is rinsed (e.g., as may occur during certain CMPprocesses). Pad rinsing may also or alternatively be modified to limitthe extent of slurry 110 dilution within the channels 1004, 1006, 1024,for example, by: (i) eliminating rinsing steps from the CMP process,(ii) reducing pad rinse times, (iii) performing rinsing steps at highrotational speeds (e.g., of the platen 104 of FIG. 1) such that therinse fluid (e.g., solvent, water, or the like) is removed from thesurface rapidly, or any combination of these and any other appropriateapproaches.

Methods of preparing Polishing Pads

FIG. 11 illustrates an example process 1100 for preparing a CMP pad 102according to an illustrative embodiment of the present disclosure. Inthis example, a plurality of thin layers of pad material areprogressively formed using a vat-based additive manufacturing process.Each layer of the plurality of layers may be formed via UV-initiatedreaction of a precursor material to form a thin layer of solidified padmaterial. The resulting pad 102 is thus formed with a preciselycontrolled structure (e.g., to achieve the compressibility and densityproperties described above) by projecting an appropriate pattern oflight (e.g., UV irradiation) for forming each thin layer. Using process1100, polishing pads 102 can be formed with more tightly controlledphysical and chemical properties than is possible using conventionalprocesses. For example, using process 1100, CMP pads 102 can be preparedwith the unique groove and channel structures described above withrespect to FIGS. 5A-10B. Process 1100 also facilitates increasedmanufacturing throughput than is possible using conventional methods,including extrusion-based printing processes (e.g., processes involvinga mechanical printhead with nozzles that eject precursor material onto asurface as the printhead is moved).

As shown in FIG. 11, at step 1102, one or more precursors, a porogen,and/or any additives are added to a vat or reservoir of an additivemanufacturing apparatus. The precursor is generally a liquid and may beor include a polyurethane or polyacrylate resin. For example, theprecursors may include one or more flexible polyurethanes, rigidpolyurethanes, elastomeric polyurethanes and urethane methacrylates.Without limitation, examples of suitable resins for the precursorinclude EPU40, EPU41, RPU60, RPU61, RPU70, UMA90 and FPU50 (availablecommercially from Carbon 3d, Redwood City, Calif.). In some embodiments,a precursor may include two or more components. For example, an exampleresin may include a first component (e.g., an A component) and a secondcomponent (a “B” component). A manufacturer of the resin may providerecommendations for preparing the resin via combination of apredetermined ratio of the first and second components of the resin. Insome embodiments, the precursors may include only one component of agiven resin. For example, the a “dual-cure” resin may include an Acomponent and a B component, which may be mixed a manufacturer-specifiedratio. This disclosure recognizes that the exclusion of one component ofa dual-cure resin may provide improved properties (e.g., in terms ofremoval rate during polishing) to the resulting polishing pad 102 (seeTABLE 2 and corresponding description below).

To adjust the properties of the polishing pad, the polyurethane resinmay be combined with one or more additives. Suitable additives include,but are not limited to, urethane monomers, urethane oligomers, aminespolyurethane with desired mechanical properties for the polishing pad102. The polyurethane resin precursor may include a photoinitiator forinitiating this polymerization reaction in regions exposed to light(e.g., UV irradiation). The precursor mixture may include a crosslinkingagent such as an isocyanate compound. Alternatively, a multi-functionaloligomer (e.g. a multi-functional urethane acrylate oligomer) may beused to improve the crosslinking degree of the urethane segment.

As described above, in some embodiments, one or more porogens isincluded in the vat or reservoir in order to form pores in the polishingpad 102 (see FIG. 3 and corresponding description above). Exampleporogens are described above. The porogen is typically added at a weightpercentage of between 1% to 30%. However, the porogen may be added at alower or higher concentration as appropriate for a given application.

At step 1104 of example method 1100, a build platform of the additivemanufacturing apparatus is lowered into a thin film of the precursormaterial until it is close to or touching the bottom of theprecursor-filled vat. At step 1106, the build platform is moved upwardto the desired height for the first layer of the pad 102. The height maybe on the scale of about 5, 10, 15, 20, 25, 50, 100 or micrometers (orgreater when appropriate). Overall, a thickness of each layer of theplurality of layers may be less than 50% of a total thickness of thepolishing pad 102 or the polishing layer 202 of the pad 102. A thicknessof each layer of the plurality of layers may be less than 1% of a totalthickness of the polishing pad 102 or the polishing layer 202 of the pad102. Moreover, as described above, an adhesive (e.g., a platen adhesive)may be placed on the build platform before the start of process 1100 sothat the pad is prepared directly on this adhesive.

At step 1108, which may be performed simultaneously with step 1106, alight source is used to “write” the structure of the first layer of thepad. For example, UV light may pass through a window at the bottom ofthe vat that is substantially transparent to the UV light (i.e.,sufficiently transparent to UV light such that the intensity of the UVlight can initiate a photoinitiated reaction of the precursor). In anexample case where the process 1100 employs continuous liquid interfaceproduction, UV light passes through a “dead zone” (i.e., the thin liquidfilm of uncured precursor between the window and the build platformwhere dissolved oxygen levels inhibit the free radical reaction) and isprojected in a predetermined pattern (i.e., a “write” pattern) forachieving a desired structure for the layer (e.g., with an appropriatelypatterned structure, as described above). In general, the regions of theprecursor that are exposed to the UV light (i.e., based on a “write”pattern) under appropriate reaction conditions are radicallypolymerized. Photo-radical polymerization occurs after exposure to theUV light. Photo-radical polymerization may proceed continuously as thebuild platform is raised. For example, photo-radical polymerization mayoccur after exposure to the UV light. Using process 1100, a CMP pad 102can be produced with the buried grooves and/or channels, described abovewith respect to FIGS. 5A-10B. The patterns of grooves and channels maybe controlled by the pattern of the UV light projected on each layer ofprecursor during step 1108. These patterns can be controlled by acomputer aided design (CAD) program that is used to design the patternof the projected UV light.

At step 1110, a determination (e.g., by a controller or processor of theapparatus) is made of whether a desired pad thickness has been achieved(e.g., that a desired number of layers of the precursor has beenphoto-radically polymerized). If the desired thickness is not reached,the process returns to step 1106 and the build platform is moved upwardagain to the desired height of the second layer, which may be the sameas or different than the height of the first layer. As the buildplatform is moved upward, uncured precursor flows beneath the curedlayer. In some embodiments, the process pauses to allow an appropriatevolume of precursor to flow (e.g., determined by the diameter of thepolishing pad 102 being manufactured and the viscosity of theprecursor). Steps 1108 and 1110 are then repeated to write and cure thesecond layer of the polishing pad 102 which may include the same or adifferent structure (e.g., of grooves and/or channels) than the firstlayer. Steps 1106 through 1110 are repeated until a desired thickness ofthe polishing pad 102 or of a portion (e.g., the backing portion 204 orpolishing portion 202) of the pad 102 is achieved.

Once the desired thickness is achieved, the process 1100 proceeds tostep 1112. At step 1112, a determination is made (e.g., by an individualor by a processor of the additive manufacturing apparatus) of whetherthe entire polishing pad 102 is complete. For example, in the precedingsteps, only the backing portion 204 of the pad 102 may have beenprepared (see FIGS. 2A-2C for reference). In such a case, it isdetermined that the final portion of the pad 102 is not complete (i.e.,because the polishing portion 202 still needs to be prepared). If thefinal portion of the pad 102 is complete, the process 1100 proceeds tostep 1118 (described below). However, if the final portion of the pad isnot complete, the process 1100 proceeds to step 1114.

At step 1114, a determination is made of whether the next portion of thepad 102 (e.g., the polishing portion 202) should be prepared in the samevat or in a different vat. For example, if the polishing portion 202 isto be prepared using the same mixture of precursor(s), porogen(s),and/or additive(s) that was introduced at step 1102, then the polishingportion 202 is to be prepared in the same vat. If the next portion ofthe pad 102 is to be prepared in the same vat, the process 1100 mayreturn to step 1102 such that the next portion (e.g., the polishingportion) of the pad 102 is prepared. However, if the next portion of thepad 102 is not to be prepared in the same vat, the process 1100 mayproceed to step 1116 where the pad 102 is moved to a second reservoir orvat. For example, the pad 102 (or the portion prepared at this stage ofthe process 1100) may be removed from the vat of the first additivemanufacturing apparatus and moved to the vat of a second additivemanufacturing apparatus. The vat of the second additive manufacturingapparatus may be filled with the appropriate combination ofprecursor(s), porogen(s), and/or additive(s) for achieving desiredproperties of the next portion (e.g., the polishing portion 202) of thepad 102. The process 1100 may then repeat from step 1104 to prepare thenext portion (e.g., the polishing portion 202) of the pad 102.

Once the desired pad thickness is achieved (step 1110) and the final padportion is complete (step 1112), the process proceeds to step 1118. Atstep 1118, the pad 102 is removed from the build platform and,optionally, cured (e.g., at an increased temperature). In someembodiments, the pad 102 is removed from the build platform and nofurther curing is performed.

At step 1120, the pad 102 may be rinsed to remove residual precursor,porogens, and/or additives. In some embodiments, the pad 102 is onlyrinsed with a mild solvent or water to prevent damage to the pad 102. Insome embodiments, the pad 102 is not rinsed at step 1114. In someembodiments, portions of the CMP pad 102 may be backfilled with a secondmaterial (e.g., as illustrated in FIG. 8E). At step 1122, the CMP pad isused for chemical mechanical planarization. For example, the CMP pad 102may be used in the system 100 described above with respect to FIG. 1.

In general, the width of the polishing pads 102 described herein is notlimited to the size of the reservoir or vat used for their preparation.During production, precursor must be continuously replenished in theregion beneath the pad that is being prepared. Polishing pads aretypically 20-30 inches in diameter and sometimes only about 1/16^(th) ofan inch thick, and more time is required to replenish the dead zone fora large-diameter polishing pad. One embodiment of the process describedherein provides a solution to this problem by facilitating theproduction of the polishing pad in a fluted, or folded, manner. In thisembodiment, the pad is constructed such that it resembles a flutedfilter paper (i.e., a circular piece of paper folded in anaccordion-like fashion). Thus, the polishing pad can be manufactured ina conical shape with folded sides, such that, while the constructed padremains pliable enough to be manipulated (e.g., before it is fullycured), the conical structure can be unfolded to achieve the desiredcircular or disk-like shape of the polishing pad.

FIG. 12A illustrates the continuous liquid interface productiondescribed above in which the pad 102 is prepared on the build platformin a horizontal configuration. Pad 102 preparation in this horizontalorientation may be referred to as a horizontal process. In yet anotherembodiment of the invention, the polishing pads 102 are produced in avertical orientation with respect to the build platform (i.e., using avertical process), as illustrated in FIG. 12B. In this embodiment,replenishment of uncured precursor resin may be controlled more readilysuch that less time is required to replenish the uncured precursor resinthan is required for a horizontal process. Tests indicate that similarperformance (e.g., in terms of removal rate during planarization) can beachieved using pads prepared in both the horizontal configuration ofFIG. 12A and the vertical configuration of FIG. 12B.

Using process 1100, in either a horizontal or vertical process, apolishing pad 102 can be produced with complex patterned structures thatare determined by the pattern of the UV light projected on each layer ofprecursor. These patterns can be controlled by a computer aided design(CAD) program that is used to design the pattern of the projected UVlight. An advantage of this approach is that the build volume (i.e., thevolume of the produced polishing pad layer) can be much larger than thevolume of the vat itself, and only enough precursor is required at agiven time to maintain a thin film in the vat. In addition to thepattern of the UV irradiation, other parameters can be changed toachieve desired properties of the cured material including: theintensity of the UV irradiation, the temperature of the vat, and theproperties of the precursor (e.g., via the addition of porogen and/oradditives).

The disclosure eliminates the need for making expensive andtime-consuming molds, as needed in molding or casting processes. Incertain embodiments, the steps of molding, casting, and machining may beeliminated. Additionally, tight tolerances can be achieved due to thelayer-by layer manufacturing approach described herein. Also, one systemcan be used to manufacture a variety of different polishing pads, simplyby changing the UV “write” pattern stored in a CAD program. Whilecertain examples herein describe the use of continuous liquid interfaceproduction as a vat-based additive manufacturing approach, it should beunderstood that any appropriate vat-based manufacturing approach may beemployed to prepare the CMP pads 102 described in this disclosure.

Experimental Examples

Effect of Porogen Amount and Extent of Crosslinking

A series of pads were prepared using the same resin combined withdifferent amounts of a porogen and with different extents ofcrosslinking. Different extents of crosslinking were achieved by eitheradding or not adding a cross-linking agent (e.g., an isocyanatecrosslinker). Highly crosslinked resin was prepared with thecross-linking agent present. A relative removal rate was determined foreach pad. The relative removal rate corresponds to the rate at which asilicon oxide layer is removed using the pad compared to the rateachieved using a commercially available CMP pad. TABLE 1 below showsthat for the same resin (FPU50), the relative removal rate is increasedwhen the amount of porogen is increased and the extent of crosslinkingis increased. In TABLE 1, a low porogen amount corresponds to about 3 wt% porogen in the precursor mixture, and a high porogen amountcorresponds to about 5 wt % of the porogen in the precursor mixture.

TABLE 1 Effect of extent of crosslinking and porogen amount on removalrate Resin Porogen amount Relative removal rate FPU50 Low 64% FPU50 High74% FPU50, Highly crosslinked Low 74% FPU50, Highly crosslinked High 81%

Effect of Omitting Component from Dual-Cure Resin

A series of pads were prepared using a dual-cure resin. For some pads,each component of the dual-cure resin was included in the precursor. Forother pads, one component of the dual-cure resin was omitted from theprecursor. TABLE 2 below shows the relative removal rates achieved bypads with different resins (or combinations of resins) with and withoutthe dual cure component included in the precursor. As shown in TABLE 2,the removal rate increased when a dual cure component was omitted fromthe precursor. In particular, pads prepared without the dual curecomponent had an increased removal rate compared to that of thecommercially available polishing pad used as a benchmark.

TABLE 2 Effect of omitting component of dual-cure resin on removal rateResin Relative removal rate FPU50 (omit dual cure component) 109% FPU50 81% FPU50/EPU40 80/20 (omit dual cure component) 110% FPU50/EPU40 60/40 80%

Modifications, additions, or omissions may be made to the systems,apparatuses, and methods described herein. The components of the systemsand apparatuses may be integrated or separated. Moreover, the operationsof the systems and apparatuses may be performed by more, fewer, or othercomponents. The methods may include more, fewer, or other steps.Additionally, steps may be performed in any suitable order.Additionally, operations of the systems and apparatuses may be performedusing any suitable logic. As used in this document, “each” refers toeach member of a set or each member of a subset of a set. Herein, “or”is inclusive and not exclusive, unless expressly indicated otherwise orindicated otherwise by context. Therefore, herein, “A or B” means “A, B,or both,” unless expressly indicated otherwise or indicated otherwise bycontext. Moreover, “and” is both joint and several, unless expresslyindicated otherwise or indicated otherwise by context. Therefore,herein, “A and B” means “A and B, jointly or severally,” unlessexpressly indicated otherwise or indicated otherwise by context.

The scope of this disclosure encompasses all changes, substitutions,variations, alterations, and modifications to the example embodimentsdescribed or illustrated herein that a person having ordinary skill inthe art would comprehend. The scope of this disclosure is not limited tothe example embodiments described or illustrated herein. Moreover,although this disclosure describes and illustrates respectiveembodiments herein as including particular components, elements,feature, functions, operations, or steps, any of these embodiments mayinclude any combination or permutation of any of the components,elements, features, functions, operations, or steps described orillustrated anywhere herein that a person having ordinary skill in theart would comprehend. Furthermore, reference in the appended claims toan apparatus or system or a component of an apparatus or system beingadapted to, arranged to, capable of, configured to, enabled to, operableto, or operative to perform a particular function encompasses thatapparatus, system, component, whether or not it or that particularfunction is activated, turned on, or unlocked, as long as thatapparatus, system, or component is so adapted, arranged, capable,configured, enabled, operable, or operative. Additionally, although thisdisclosure describes or illustrates particular embodiments as providingparticular advantages, particular embodiments may provide none, some, orall of these advantages.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. The use ofany and all examples, or exemplary language (e.g., “such as”) providedherein, is intended merely to better explain the disclosure and does notpose a limitation on the scope of claims.

What is claimed is:
 1. A chemical mechanical polishing pad, comprising:a polishing portion formed using a vat-based additive manufacturingprocess, the polishing portion comprising a polymer material with afirst elastic modulus.
 2. The chemical mechanical polishing pad of claim1, further comprising a backing portion, wherein the polishing portionis disposed on the backing portion.
 3. The chemical mechanical polishingpad of claim 2, wherein the backing portion has a second elasticmodulus.
 4. The chemical mechanical polishing pad of claim 3, whereinthe second elastic modulus is less than the first elastic modulus. 5.The chemical mechanical polishing pad of claim 1, wherein the polishingportion comprises a polishing surface, the polishing surface comprisingat least one of grooves, pores, or a microstructure.
 6. The chemicalmechanical polishing pad of claim 2, wherein the backing portion isformed using the vat-based manufacturing process.
 7. The chemicalmechanical polishing pad of claim 2, wherein the backing portioncomprises at least one of a nonporous layer, a porous layer, or alattice structure.
 8. The chemical mechanical polishing pad of claim 2,wherein the polishing portion and the backing portion are attachedwithout the use of an adhesive.
 9. The chemical mechanical polishing padof claim 1, wherein a density of the polishing portion is in a rangefrom 0.3 to 0.9 grams per centimeter cubed.
 10. The chemical mechanicalpolishing pad of claim 1, wherein the polishing portion comprisespolyurethane.
 11. A method of making a chemical mechanical polishingpad, the method comprising: providing a precursor to a first vat of afirst additive manufacturing apparatus; and preparing at least a portionof the chemical mechanical polishing pad via a layer-by-layer process byexposing the precursor to patterned light, the prepared portioncomprising a polymer material with a first elastic modulus.
 12. Themethod of claim 11, wherein the precursor comprises a resin and one orboth of a porogen and a crosslinking agent.
 13. The method of claim 12,wherein the resin is one component of a multiple component dual cureresin.
 14. The method of claim 12, wherein a concentration of theporogen is in a range from one to thirty percent by weight.
 15. Themethod of claim 12, wherein the crosslinking agent is an isocyanatecompound.
 16. The method of claim 11, wherein: the prepared portion is abacking portion of the chemical mechanical polishing pad; and the methodfurther comprises: removing the backing portion from the first vat;affixing the prepared portion to a surface within a second vat of asecond additive manufacturing apparatus; providing a second precursor tothe second vat of the second additive manufacturing apparatus; andpreparing a polishing portion of the chemical mechanical polishing padby exposing the second precursor to patterned light, the preparedpolishing portion comprising a polymer material with a second elasticmodulus, wherein the first elastic modulus is less than the secondelastic modulus.
 17. The method of claim 16, wherein the backing portioncomprises at least one of a nonporous layer, a porous layer, or alattice structure.
 18. The method of claim 16, wherein the polishingportion comprises a polishing surface, the polishing surface comprisingat least one of grooves, pores, or a microstructure.
 19. The method ofclaim 16, wherein a density of the polishing portion is in a range from0.3 to 0.9 grams per centimeter cubed.
 20. The method of claim 11,wherein: the prepared portion is a polishing portion of the chemicalmechanical polishing pad; and the method further comprises: removing thepolishing portion from the first vat; attaching the prepared portion toa backing portion, wherein a second elastic modulus of the backingportion is less than the first elastic modulus of the polishing portion.